'74 CB383 (CB360) - a Mighty Mouse adventure bike

oh haha i meant piston rings

It's crazy how much your thread is coinciding with my build, I just got my reamer delivered to me today (7mm high speed steel spiral flute style...i think) I'll try it out tonight on my new valve guides and see how it all works with standard valves
 
Actually, you only need 1mm OS intakes if your doing 1mm OS exhaust.
As the exhaust is the major restriction on 360, maybe 1mm OS would wake it up a bit more?
 
I emailed a guy in CA selling valve guides and making valves. He sells the guides with viton seals (which I already bought before I knew the valves were bad). He agreed to cut me a good deal combining the guides and valves with no seals.

Also, I can't find a single instance (on the net) of someone putting in 1mm oversized intake/exhaust valves on a CB360. I know someone, somewhere has to have done it, but its not been posted so far as I can tell. Anyone have a link or seen it up?

This lack of information sweetens the notion of trying it out. And then sharing the results. I may have to put this bike on a dyno when I get it tuned up. You are a (bad) influence, PJ. :p

As far as I can tell, new seats aren't required. (any contradictions on that?) I just need to have them machined. Already talked to a local guy interesting in doing that.
 
Also, can anyone recommend a good source for a full set of different jet sizes at a decent price?
I remembered, again, that since I moved from 5,000ft elevation to sea-level in addition to the engine rebuild I will need to start from jetting scratch.
Might as well just get a full set so I can play with them without having to order a bunch in sequence.
 
Stock jetting will probably be close @5,000ft
Brendon is now up to 125 secondary mains, but, we are at sea level (although it rained so much today it felt like we were below it ;D )
Sonrier fitted OS valves in his 378

http://www.dotheton.com/forum/index.php?topic=19672.475
 
Not too much rain here in Anchorage. Plenty of snow, though it got nice and warm today. I think a high of 37*f :eek:

Tinkered around with a few items today since I can't finish the head. Put new bearings in the wheels. Took off my old rear sprocket and replaced it with a new one. The new swingarm requires a longer chain, so both sprockets are getting swapped.

I was running stock front and a 35T rear. New rear is back to the stock 34T. For the front I got a 17T and an 18T just to play with and see if it is too tame, or if it works well on the highway.

Anyhow, if you've ever wondered what the difference in diameter one tooth makes between the 34T and 35T at this size, its about 10mm
CB383Valves-6_zpsfc06781f.jpg



Spent a good couple of hours slowly opening up the exhaust ports and trying to get them roughly the same. I took more out of the sides, and shaved a lot of the excess off the guide protrusion, then quite a bit off the bottom curve opposite the guides (shortest pathway for the exhaust gases to take). Ran out of grinder stone bits so the one still needs to be cleaned up a wee bit.
CB383Valves-2-2_zps5024b4ae.jpg

CB383Valves-3-2_zps7fc2bf18.jpg

CB383Valves-4-2_zps6e3c82f8.jpg


Also took a fair amount out just behind the valve seat, but couldn't get a good angle for a photo.

Any feedback?

I've never ported a head before.
 
You should have left most of the bottom of port in position and made it more 'D' shape (next time ;D )
Opening up all the way around won't harm high rpm but you loose a little mid range (not that you had much to start with ;D )
 
Ah! Thanks, PJ. Always trying to learn.

I was focusing on the sides at first but with the header studs in the way I was having a hard time getting as much material off as I wanted. I guess I got a little impatient and just went all the way around. Doh! (Homer Simpson voice with a palm to the forehead)

Hopefully with all said and done, it will still be a bit "better," if not ideal.

I am realizing sadly that today is my last day to tinker for a while. Back to work tomorrow until March 15, then off to HI for a week long photo job (other work, I guess), then to Utah for a friend's wedding. Hopefully back in Anchoragua by March 25. Damn. Nearly a straight month of motorcycle abstinence. CHEAP.
 
Are you clearing out the junk or actually removing metal? Thinking about doing this to mine since i havent assembled it fully yet.

Reason for doing this is better air flow?
 
Actually removing metal.

(Disclaimer to me sounding like I know what is going on: All of my knowledge of this is from reading others' experience and various forums, most of the concrete knowledge from PJ)

The exhaust ports are the main restriction on flow through the 360's engine. As you have probably read, a lot of unaware folks buy 360's and try to put Mikuni VM32s and such on them with resulting headaches. The Stock carbs and intake ports are already a bit large for the stock engine, so boring the cylinders out for bigger displacement helps bring those into a more optimal size for the flow.

I think this is opposite to the 350, which gets help from larger carbs and intake ports. I may be wrong on this, as I've never owned one, but I am pretty sure I've read about that (and it is probably where most people get the notion to do it on 360's).

So I ground off much of the protruding valve guide boss, and opened it up around the perimeter. I would say if you have the head off, definitely do this. Just do it better than I did and go for the D shape. ;D

Should help exhaust flow more efficiently out of the combustion chamber. I am also making a straight through exhaust set up to help with this.

and thanks, 3DogNate!
 
Nate just made a comment saying this was a cool project. Not sure if he has porting info?

I would maybe ask PJ or Sonreir if they have any photos of the porting they have done. Or just look at mine, but take less off the bottom and more off the sides.
 
The bottom being the lump where the guide is?

Are you just taking material from the mouth or the opening or all the way in?
 
I'll see if I can find pic online (maybe I took some of mine, can't remember)
from combustion chamber, bowl behind valve head fully smoothed out
CB360head.jpg


Intake
CB360headport2.jpg


Looking for exhaust pic, although if you can imagine exhaust flat where the picture is cut off, that's the 'D' shape, blend into the bowl area
OK, couldn't find a pic so I just took one of head I'm going to work on.
Line is a bit high but you get the idea, maybe 2/3~3/4 the way down
360exhaustport.jpg
 
Those are great, PJ.

I'm thinking I may go back and work on mine a bit more. Bring that D section to the gasket. Or do you think that would be too much with what I have already done?
 
restricting it with a steel 'D' gasket probably won't be a good idea, just open the top half to original squashed gasket size
 
Finally back in Anchorage. Went down to Hawai'i for a few days after work to meet a friend. Sitting in the cockpit jumpseat on a return flight from Honolulu to LA, I had an awesome conversation about classic motorbikes with the captain. Turns out he is very close friends with Eddie Lawson and invited me down to ride with them. Said he had a bunch of extra bikes. Sounds like a fun way to get killed.

Anyhow. On to bike progress.


-dropped off the tank and side covers to get paint. Really excited the see them finished, especially after meeting the guy who was recommended to me for the job. His work is fantastic.

- installed new valve guides. Really wasn't much too it. I heated the head to about 200* for a bit, and the old tapped right out. Swapped the circlips, and the new ones tapped right in.

-reamed the valve guides. (Thanks Finnigan)

-dropped the head and +1mm oversized valves off at Alaska Drag Bike to have them seated.


With the oversized valves, will I need to check piston-valve clearance? I did not skim the head at all.
 
Also this

http://youtu.be/ojVsXB12zC8

reminds me of going to see Barnum and Bailey as a kid.
 
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